Undeclaring gives a unit back the state it was found in, and removes a process the mesh made (hq ADR 0118, issue 130)

A service undeclared used to be stopped: unassigning the private network stopped the container
runtime, unassigning sshd would stop ssh, an uplink module would take the machine offline. The
host now records the unit's state when it first applies it and restores that on undeclare —
found running stays running; started by the mesh (the converge filter) is stopped again; nothing
is started on the way out; a pre-existing record leaves the unit alone.

An undeclared process had no removal at all and failed every apply on its node; its unit, timer
and bundle are now removed.

internal/store/store.go

@@ -82,6 +82,13 @@ type Applied struct {
 	// service removed as if it had a state is stopped: the machine's network manager, for one.
 	Stateless bool `json:"stateless,omitempty"`
 
+	// Found is, for a service, the state its unit was in when this host first applied it — before
+	// the mesh started, stopped, enabled or disabled anything. Removal gives that back and nothing
+	// more (novox/hq ADR 0118): a unit that was running before the mesh arrived keeps running
+	// when its declaration goes; one the mesh started is stopped again. Absent on a record written
+	// before the host kept it, and then the unit is left exactly as it is.
+	Found *FoundUnit `json:"found,omitempty"`
+
 	// Into is set for a file written into rather than over (novox/hq ADR 0102): the format, what
 	// each of the mesh's keys held before it set them, which of them were absent, and whether the
 	// file itself was — so undeclaring it gives the machine back exactly what it had.
@@ -447,3 +454,12 @@ func originOf(r Applied) string {
 	}
 	return r.Origin
 }
+
+// FoundUnit is a service's unit as the host first found it.
+type FoundUnit struct {
+	// State is "running" or "stopped".
+	State string `json:"state"`
+	// Boot is "enabled" or "disabled" — or empty when the declaration never set it, and the host
+	// never touched it.
+	Boot string `json:"boot,omitempty"`
+}